The primary method of extracting bitumen from pit-mined oilsands is by hot water extraction. That is, oilsands are slurried with hot water to solubilize entrained petroleum to some degree, and to permit transport by pipeline to an extraction plant, where the slurry is separated into fractions for recovery and processing of bitumen. This process consumes multiple barrels of fresh water per barrel of oil produced and generates a high volume of waste that is difficult to treat prior to release. Long term use of hot water extraction for high output oil production raises concerns about both water management and environmental impact. Furthermore, the bitumen fraction recovered by this method remains highly viscous and must further be diluted with solvents prior to further pipeline transport.
Bitumen is generally recovered for upgrading by skimming of froth from the aforementioned slurry, followed by cracking of the bitumen froth into smaller hydrocarbon fractions. Thermal cracking, hydrocracking, and catalytic cracking and are all common methods for upgrading.
Synthetic zeolites are widely used as cracking catalysts in fluid catalytic cracking and hydro-cracking processes. Zeolites have an open structure with small, regular pores capable of accommodating a wide variety of cations for ready exchange in solution. These pores are also suitable for confining and filtering molecules. The hydrogen form of zeolites (prepared by ion-exchange) are powerful solid-state acids, and can facilitate a host of acid-catalyzed reactions, such as isomerisation, alkylation, and cracking. In the petroleum industry, crude oil distillation fractions may be heated in a furnace and passed to a reactor, where the crude is exposed to the zeolite catalyst. Several reactors may be used at varying temperatures until adequate separation is achieved. Hydrogen and synthetic catalyst are generally recycled.
Chabazite, a natural zeolite with platy morphology and a highly acidic surface, is a proven cracking catalyst and a natural sorbent. Kuznicki et al (Apr. 2, 2007, “Natural zeolite bitumen cracking and upgrading”; Microporous and Mesoporous Materials 105; 268-272) showed that natural zeolites such as chabazite may be modified to produce strong acids, and that such acids could be used to catalyze cracking of bitumen in raw oilsand samples with minimal coking. The resulting petroleum fractions were then extracted with toluene to produce a less viscous bitumen fraction.
U.S. Pat. No. 4,596,651 describes a process for extracting bitumen from tar sands using solvents. Specific and non-specific solvents are used in series to obtain bitumen low in fines and asphaltenes. For example, tar sands may first be slurried with a nonspecific solvent to dissolve most of the available bitumen, and then a specific solvent is added to precipitate the asphaltenes and fines from the slurry.
U.S. Pat. No. 4,036,732 discusses solvents that may be employed in the extraction of bitumen and asphaltenes from oilsands. Fresh tar sands are initially slurried with small amounts of water or an aqueous phenol solution, and paraffinic solvents such as pentane may be used to separate desirable bitumen from asphaltenes.
U.S. Pat. No. 3,941,679 describes a waterless bitumen extraction method. Raw oilsands are mixed with a non-aqueous extraction solvent that contains trichlorofluoromethane. The solvent must then stripped from the fluid phase to isolate the hydrocarbonaceous substances.
U.S. Pat. No. 6,412,557 describes an in situ bitumen recovery and upgrading process from deep oilsands. An upright combustion front is initiated from a vertical injection well and is propagated laterally across an oilsands formation towards a production well. The production well has a horizontal leg extending towards the injection well so as to be in the path of the combustion front. A hydrocracking catalyst is embedded within the horizontal leg such that the hot combustion gases react with oil over fresh catalyst as the combustion front advances, providing in situ upgrading during production.